Complete content for NetCDF guide

[vmartinez-cu]

The NetCDF guide was created pulling content written by Doug Lindholm in Confluence. Confluence page

Some additional content is needed to provide context and explain how this file format is being used at LASP. I added a warning at the top of the guide noting that it's incomplete.

Details still needed:

Expand overview section and explain bullet points
Expand purpose section
Expand on options available
Expand on how to apply the guide
Include information for compliance checkers, especially since this is the convention being pushed by the NASA Earth Science Data Systems and that changes what's required vs. useful attributes